The present invention relates to a water-resistant switching device and more particularly but not exclusively to an entry transmitter for a vehicle including such a switching device.
It is increasingly a requirement to provide electrical switching capable of being operated under damp conditions, for example in the open air when it is raining. In the case of entry transmitters for vehicles, which commonly use radio frequency or infra-red transmitters to operate entry systems for the corresponding vehicle, manufacturers are seeking increasing levels of waterproofing with current requirements ranging from 0.3 to 6 metres.
Prior art techniques to provide waterproofing in water-resistant switching devices include the use of an xe2x80x9cOxe2x80x9d ring seal, with pressure on the seal being maintained by, for example screws an overall elastomer keypad with the edge of the keypad crushed between two plastic elements and maintained there by clips, or by overmoulding the seal with elastomer.
These techniques have a number of defects, including the relatively high cost and difficulty of assembling when using screws and metal inserts, and the likelihood of plastic clips failing over long durations and high temperatures.
It is an object of the present invention to at least partially mitigate the difficulties of the prior art.
According to a first aspect of the present invention there is provided a water-resistant switching device having a casing, the casing having first and second parts, said first part having a base wall and a peripheral edge wall, said device further comprising an elastomeric body extending along said base wall and forming an upstanding rib portion, wherein said rib portion is spaced from and co-operates with a portion disposed on the inside of side peripheral edge wall to receive a counterpart flange portion of the second part of said casing.
Preferably said counterpart flange portion has a thickness greater than said spacing, whereby when said counterpart flange portion of said second casing part is engaged with said portion, said rib portion resiliently grips said counterpart flange portion.
Conveniently said portion is part of said elastomeric body and forms an inwardly-directed flange portion from said peripheral edge wall, and said counterpart flange portion has an outwardly-directed lip for co-operation with said inwardly-directed flange portion.
Conveniently said portion is part of the peripheral edge wall and forms an inwardly-directed flange portion from said peripheral edge wall, and said counterpart flange portion has an outwardly-directed lip for co-operation with said inwardly-directed flange portion.
Conveniently said elastomeric body is secured to said first part of said casing.
Advantageously said elastomeric body is secured by overmoulding.
Conveniently said casing contains a circuit device, and said first part of said casing is an operating member for said circuit device.
Advantageously said casing contains a battery, and said first part of said casing is removable for changing said battery.
According to a second aspect of the present invention there is provided an entry transmitter for a vehicle comprising a water-resistant switching device according to the first aspect of the present invention.